Twizeyimana Mathias, Hammer Philip E, Gachango Esther, Craig Kelly, Espejo Billie, Biggs Matthew B, Kremer James, Ingham David J
Research and Development, AgBiome, Inc., Research Triangle Park, NC, United States.
Front Plant Sci. 2023 Feb 1;14:1080116. doi: 10.3389/fpls.2023.1080116. eCollection 2023.
The management of soybean rust (SBR) caused by the obligate fungus mostly relies on the use of synthetic fungicides, especially in areas where the disease inflicts serious yield losses. The reliance on synthetic fungicides to manage this disease has resulted in resistance of populations to most fungicides. In this study, bacteria isolated from diverse environments were evaluated for their biocontrol potential against using soybean detached-leaf method and on-plant in the growth chamber, greenhouse, and field. Among 998 bacterial isolates evaluated using the detached-leaf method; 58% were isolated from plant-related materials, 27% from soil, 10% from insects, and 5% from other environments. Of the isolates screened, 73 were active (they had ⪖ 75% rust reduction) with an active rate of 7.3%. From the active isolates, 65 isolates were re-tested on-plant in the growth chamber for activity confirmation. In the confirmation test, 49 bacteria isolated from plant-related materials maintained their activity with a confirmation rate of 75%. The majority of bacteria with confirmed activity belonged to the taxonomic classes Bacilli and Gammaproteobacteria (70%). Active isolates were prioritized for greenhouse and field testing based on activity in the initial screen and confirmation test. Six bacterial isolates AFS000009 (), AFS032321 (), AFS042929 (), AFS065981 (), AFS090698 (), and AFS097295 () were selected from those bacteria that maintained activity in the confirmation test and were evaluated in the greenhouse, and five among them were evaluated in the field. From the Alabama field evaluation, all bacterial isolates reduced rust infection as well as azoxystrobin (Quadris at 0.3 L/ha) used as the fungicide control ( > 0.05). Moreover, the scanning electron micrographs demonstrated evidence of antagonistic activity of AFS000009 and AFS032321 against urediniospores. Bacterial isolates that consistently showed activity comparable to that of azoxystrobin can be improved through fermentation and formulation optimization, developed, and deployed. These bacteria strains would provide a valuable alternative to the synthetic fungicides and could play a useful role in integrated disease management programs for this disease.
由专性真菌引起的大豆锈病（SBR）的防治主要依赖于合成杀菌剂的使用，尤其是在该病导致严重产量损失的地区。依赖合成杀菌剂来防治这种病害已导致病原菌群体对大多数杀菌剂产生抗性。在本研究中，利用大豆离体叶片法以及在生长室、温室和田间对植株进行试验，评估了从不同环境中分离的细菌对大豆锈病的生物防治潜力。在使用离体叶片法评估的998株细菌分离物中，58%分离自与植物相关的材料，27%分离自土壤，10%分离自昆虫，5%分离自其他环境。在筛选出的分离物中，有73株具有活性（锈病减少率≥75%），活性率为7.3%。从具有活性的分离物中，选取65株在生长室对植株进行重新测试以确认活性。在确认试验中，49株从与植物相关材料中分离的细菌保持了活性，确认率为75%。大多数具有确认活性的细菌属于芽孢杆菌纲和γ-变形菌纲（70%）。根据初始筛选和确认试验中的活性，对具有活性的分离物进行优先排序，用于温室和田间试验。从在确认试验中保持活性的细菌中选取了6株细菌分离物AFS000009（）、AFS032321（）、AFS042929（）、AFS065981（）、AFS090698（）和AFS097295（）在温室中进行评估，其中5株在田间进行评估。从阿拉巴马州的田间评估来看，所有细菌分离物都减少了锈病感染，与用作杀菌剂对照的嘧菌酯（0.3 L/公顷的翠贝）效果相当（P＞0.05）。此外，扫描电子显微镜照片显示了AFS000009和AFS032321对大豆锈菌夏孢子具有拮抗活性的证据。对始终表现出与嘧菌酯相当活性的细菌分离物，可以通过发酵和制剂优化进行改良、开发和应用。这些细菌菌株将为合成杀菌剂提供有价值的替代方案，并可能在该病害的综合病害管理计划中发挥有益作用。
